论文标题
使用全局麦克斯韦层摄影仪与8通道头线圈的基于磁性的电特性映射：一个模拟研究
Magnetic-resonance-based electrical property mapping using Global Maxwell Tomography with an 8-channel head coil at 7 Tesla: a simulation study
论文作者
论文摘要
目的：全球麦克斯韦断层扫描（GMT）是一种最近引入的体积技术，用于通过磁共振测量值对电性能（EP）无创估计。先前的工作使用理想的射频（RF）激发评估了GMT。这项模拟研究的目的是用现实的RF线圈评估GMT性能。方法：我们设计了一个带有$ 8 $脱钩的频道的传输RF线圈，价格为$ 7 $ t HEAD成像。我们计算了用于不同RF光滑方法的异质头模型内的RF传输场（$ B_1^+$），并将其用作GMT的输入来重建所有Voxels的EP。结果：当线圈装有不同的头部模型时，线圈调整/解耦保持相对稳定。 EP估计中的平均错误从$ 7.5 \％$变为$ 9.5 \％$和$ 4.8 \％$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $分别为相对介电和电导率的$ 7.2 \％$，而无需重新调整线圈而更改头模型时。当应用一个基于SVD的RF光滑算法时，结果略有改进，一次使用一个线圈代替激发。尽管EP出现错误，但RF传输场（$ b_1^+$）和吸收功率可以预测，整个头部都少于$ 0.5 \％$错误。 GMT可以准确检测到数值插入的肿瘤。结论：这项工作表明，GMT可以使用量身定制的8通道RF线圈设计在$ 7 $ t的情况下可靠地重建EP。未来的工作将集中于构建GMT噪声的稳健性，以实现Vivo GMT实验。意义：GMT可以提供对组织EP的准确估计，该估计可以用作生物标志物，并且可以对患者特定于RF功率沉积进行特定于患者的估计，这是超高场磁共振成像的未解决问题。
Objective: Global Maxwell Tomography (GMT) is a recently introduced volumetric technique for noninvasive estimation of electrical properties (EP) from magnetic resonance measurements. Previous work evaluated GMT using ideal radiofrequency (RF) excitations. The aim of this simulation study was to assess GMT performance with a realistic RF coil. Methods: We designed a transmit-receive RF coil with $8$ decoupled channels for $7$T head imaging. We calculated the RF transmit field ($B_1^+$) inside heterogeneous head models for different RF shimming approaches, and used them as input for GMT to reconstruct EP for all voxels. Results: Coil tuning/decoupling remained relatively stable when the coil was loaded with different head models. Mean error in EP estimation changed from $7.5\%$ to $9.5\%$ and from $4.8\%$ to $7.2\%$ for relative permittivity and conductivity, respectively, when changing head model without re-tuning the coil. Results slightly improved when an SVD-based RF shimming algorithm was applied, in place of excitation with one coil at a time. Despite errors in EP, RF transmit field ($B_1^+$) and absorbed power could be predicted with less than $0.5\%$ error over the entire head. GMT could accurately detect a numerically inserted tumor. Conclusion: This work demonstrates that GMT can reliably reconstruct EP in realistic simulated scenarios using a tailored 8-channel RF coil design at $7$T. Future work will focus on construction of the coil and optimization of GMT's robustness to noise, to enable in-vivo GMT experiments. Significance: GMT could provide accurate estimations of tissue EP, which could be used as biomarkers and could enable patient-specific estimation of RF power deposition, which is an unsolved problem for ultra-high-field magnetic resonance imaging.
